Composite reflector for two independent orthogonally polarized beams



Ska-Mun HUUI May-4m July 2, 1963 R. w. MARTIN COMPOSITE REFLECTOR FORTWO INDEPENDENT ORTHOGONALLY POLARIZED BEAMS 2 Sheets-Sheet 1 FiledApril 14, 1958 w m M AX/S OF/PEKiz I/ORIZONTAL'JKJ flIW- 3 I INVENTORROB? MAAWN ATTORNEY R. W. MARTIN TE REFLECTOR FOR TWO INDEPENDENTORTHOGONALLY POLARIZED BEAMS July 2, 1963 COMPOSI 2 Sheets-Sheet 2 FiledApril 14, 1958 I -5 a a INVENTOR ROBE/97%flA/2T/N ATTORNEY United StatesPatent 3,096,519 COMPOSITE REFLECTOR FOR TWO INDEPEND- ENT ORTHOGONALLYPOLARIZED BEAMS Robert W. Martin, Hicksville, N.Y., assignor to SperryRand Corporation, a corporation of Delaware Filed Apr. 14, 1958, Ser.No. 728,482 9 Claims. (Cl. 343-456) The invention relates to microwaveenergy directive devices and, more particularly, is concerned with acomposite microwave energy directive element which is adapted to receivetwo independent beams of orthogonally polarized microwave energy andoperative to direct said independent beams along independent paths.

Various applications exist in the art for the transmission ofindependent beams of microwave energy along respective paths which beara predetermined angular relationship with respect to each other. Onefamiliar example is the beam configuration generated for use with aV-beam height finding radar. A conventional V-beam radar antenna arrayis shown in FIG. 13.15(a) appearing on page 482 of the MIT RadiationLaboratory Series, vol. 12, edited by Samuel Silver and entitledMicrowave Antenna Theory and Design. Such an array usually comprises twoindependent microwave energy reflecting elements each of which is shapedto produce a fan-shaped reflected beam of microwave energy. One of thereflectors produces a fan-shaped beam lying in a vertical plane. Thereflector is rotated through a predetermined angle, relative to thefirst reflector, so as to produce a fan-shaped beam of microwave energylying in a plane displaced from the plane of the vertical beam by apredetermined angle, for example, 45.

The two reflectors are arranged on a common supporting pedestal andrequire at least a two-fold increase in the total structure of either ofthe reflectors when used alone. Accordingly, the physical size, weight,and profile bulk of the prior art V-beam antenna array imposeundesirable handicaps as to ease of assembly and portability, forexample, of the antenna installation.

It is the general object of the present invention to provide a microwaveenergy directive element which reduces to a minimum the physical size,weight, and profile bulk of energy directing means required to producetwo independent and spatially displaced beams of microwave energy.

A more specific object of the present invention is to provide acomposite microwave energy directive apparatus having a portion commonto the component individual microwave energy directive means whichfunction to produce two independent and spatially displaced beams ofmicrowave energy.

Another object of the present invention is to provide a superimposedpolarization isolated shaped reflector for producing fan-shaped beams ofmicrowave energy for use in a height-finding radar system.

A further object of the present invention is to provide a compositemicrowave energy reflective element comprising two electrically isolatedcomponent shaped reflectors, each conforming in part to the same surfaceof revolution.

An additional object is to provide a superimposed microwave energyreflector comprising two independently operative energy directing meanseach having respective polarization sensitive microwave energyreflecting means.

These and other objects of the present invention, as will appear morefully upon a reading of the following specification, are achieved in apreferred embodiment by the provision of a composite microwave energyreflector which may be considered as being comprised of two identicalcomponent microwave energy reflectors, each conforming in part to thesame surface of revolution. An understanding of the shape of thecomposite reflector may Patented July 2, 1963 "ice - 2 be facilitated bythe following description of the manner in which the composite reflectoris generated. The two component reflectors are at first exactlysuperimposed whereby the respective reflecting surfaces are everywherein intimate contact. Then, one of the reflectors is rotated through apredetermined angle, relative to the other, about the axis of revolutionof the surface of revolution.

In an illustrated preferred embodiment of the invention, each of thecomponent reflectors includes a first portion conformal to the sameparaboloid and a second portion which is doubly shaped so as to producea resultant beam pattern of reflected microwave energy which is narrowin one dimension and approximately cosecant-squared in shape, forexample, in a second orthogonal dimension. After the angulardisplacement of one of the component reflectors relative to the otherthrough an angle of, for example, 45, there results a compositemicrowave energy reflector, containing a surface common to the otherwiseindependent reflectors, which is suitable for application in a V-beamheight-finding radar system.

Each of the two reflectors comprising the composite reflector iselectrically isolated from the other by the use of polarizationsensitive reflecting elements. In the illustrated preferred embodiment,each of the component reflectors consists of a shaped plastic materialwhich is similar to that employed in modern lightweight radomes. Theplastic material serves as a mechanical support for polarizationsensitive reflecting elements such as, for example, flat metallicmicrowave energy reflecting strips which are bonded to the plasticmaterial. The strips are arranged parallel to each other in each of thecomponent reflectors, the strips being mounted in a horizontal directionin one and mounted in a vertical direction in the other componentreflector.

The composite reflector is irradiated by a pair of microwave energyemitting means each of which emits microwave energy which is polarizedorthogonally with respect to the other. As a result, each of thecomponent reflectors comprising the composite reflector sees only therespectively associated microwave energy emitting means so that twoelectrically independent beams of microwave energy are emitted from thecomposite reflector.

For a more complete understanding of the present invention, referenceshould be had to the fol-lowing specification and to the appendeddrawings of which:

FIG. 1A is a front and FIG. 1B is a sectional view of one of the twoidentically shaped component reflectors utilized in the compositereflector which conforms to a figure of revolution over a portion of itssurface;

FIG. 2A is a front and FIG. 2B is a sectional view of the compositereflector resulting from the rotation through a predetermined angle ofone of two identically shaped component reflectors relative to the otherabout the axis of revolution of the figure of revolution;

FIG. 3 is a front view of the composite reflector which illustrates thelocation of polarization sensitive reflecting elements associated withthe respective component reflectors;

FIG. 4 is a front elevation of the composite reflector;

FIG. 5 is a side elevation of the composite reflector of FIG. 4;

FIG. 6 is an enlarged sectional view of the composite reflector of FIG.4 taken along the line 66;

FIG. 7 is an enlarged sectional view of the composite reflector of FIG.4 taken along line 7-7;

FIG. 8 is a front elevation of the composite [reflector of FIG. 4illustrating the addition of shaped dielectric material to the lowerportions of the composite reflectors which serves to equalize theelectrical path length between the microwave energy emitting means andthe symmetrically located portions of the respectively associatedcomponent reflectors; and

FIG. 9 is a schematic diagram of a flared horn useful for irradiatingthe slanted component reflector.

FIG. 1A illustrates one of the two component rnicro wave energyreflectors which comprise the composite reflector of the presentinvention. The uppermost portion of the reflector consists of a portionof a figure of revolution which is a par-aboloid in the illustratedpreferred embodiment. The paraboloidal surface exists above thehorizontal line drawn between the numerals 1 and 2, It will be notedthat the axis of revolution of the paraboloidal surface is below theline 12. The lower portion of the reflector of FIGURES 1A and 1B, i.e.,the portion below line 12, is a double curvature reflector which actswith the upper paraboloidal portion to produce, for example, acosecant-squared beam of reflected microwave energy when irradiated. Thereflector of FIGURES 1A and 1B is generally similar to the barrel-shapedreflector well known in the art and illustrated in FIG. 13.17 of theaforementioned MIT Radiation Laboratory Series, vol. 12, page 484.

The curvature of the reflector of FIG. 1A is illustrated in the sectionof FIG. 1B taken along the line 1B1B. From the section it can be Seenthat the curvature between points 3 and 4 of the reflector is conformalto a parabola and that the curvature between the points 4 and 5 issomewhat more pronounced than that of a parabola, the latter of which isillustrated by the dotted line between points 4 and 6. The increasedlower curvature of the reflector of FIGURES 1A and 1B produces increasedhigh altitude coverage when the reflector is utilized in a ground basedheight-finding radar system.

In the generation of the composite reflector of an illustrativeembodiment of the present invention, two identically shaped reflectors,like the one illustrated in FIG- URES 1A and 1B, are first superimposedso that their respective elemental surfaces are everywhere in intimatecontact. Then, one of the reflectors is rotated about the axis ofrevolution of the figure of revolution to which a portion of eachreflector conforms. The result of such a rotation is illustrated in thecomposite reflector of FIG- URES 2A and 2B. As previously mentioned,only the uppermost portion of each component antenna of the compositereflector is conformal to a paraboloid. Therefore, upon rotation of oneof the component antennas relative to the other, the elemental surfacesof the antennas which first were everywhere in intimate contact departfrom each other. This is true because each of the component reflectorsis not completely comprised of the common figure of revolution but onlypartially so. Thus, as the angle increases through which the reflectorsare mutally displaced, the extent of the remaining common areadecreases.

Assuming, for example, that the displacement angle is 45 (commonlyemployed in V-beam height-finding antenna arrays), the remaining commonsurface area of the composite reflector is that embraced Within lines7-8-9, 910--11, 1112 and 127. In addition to this area which is commonto both component reflectors, there are also two additional andsymmetrically identical paraboloidal surface areas embraced within thelines 13- 149, 987 and 7-13 and within lines 15169, 9-1011 and 11-45.Each of these additional surfaces is not shared by both of the componentreflectors but is unique to a respective one of the componentreflectors. However, it will be noted that the common surface as well asthe two additional surfaces just described are all conformal to the sameparaboloid.

The remaining portions of the composite reflector o f FIGURES 2A and 2Bdo not lie on one surface as is indicated by the dotted peripheral linesof the rearward portions of the composite reflector. The slantedreflector intersects with the horizontally disposed reflector along theline 1217. The forward portion of the slanted reflector which isoutlined by the lines 1312, 12-17 and 171813 lies above (as viewed inFIG. 2A) the rearward portion of the horizontally disposed reflectorwhich is outlined by the lines 712, 1217 and 17197. The rearward portionof the slanted reflector which is outlined by lines 1712, 1211 and11-20-47 lies below the forward portion of the horizontally positionedreflector which is outlined by lines 17-12, 1215 and curved line15--21-17. In other words, the surfaces of the component reflectorscomprising the composite reflector merge into a common surface alon thelines 127 and 1211 and intersect along the line 1217. It should be notedthat the portion of the horizontally disposed reflector which isoutlined by the lines 12-19, 197, and 7l2 as well as the portion of theslanted reflector which is outlined by the lines 1211, 11-20, and 2012are all conformable to the same paraboloid as are the common surface andthe two additional surfaces previously described. The total conformalsurface is indicated by the diagonally-hatched portion of FIG. 2A.

The central sectional view of FIG. 2B is taken along the line 2B2B ofFIG. 2A and is illustrative of the shape of the composite reflector justdescribed. The curved line 222324 corresponds to the curved line 345 ofFIG. 1B, both representing the central section curvature of thehorizontally disposed reflector. Curved line 25- 22-23-26 represents thecentral section curvature of the slanted reflector of FIG. 2A. It shouldbe noted that the lower portion of the slanted reflector, represented bythe curved line 23-26 of FIG. 2B, lies rearward of the lower portion2324 of the horizontally disposed reflector. On the other hand, theupper portions (above point 23) of both reflectors lie along a commoncurve. The common curve is the parabola with which the commonparaboloidal surface of revolution of both the horizontal and slantedreflectors is generated.

The front view of the composite reflector illustrated in FIG. 3 showsthe orientation and location of the metallic reflecting strips which areemployed to electrically isolate each of the component reflectors fromthe other. The strips bonded to the horizontally disposed reflector arepositioned parallel to each other along horizontal lines while thestrips of the slanted antenna are positioned parallel to each otheralong vertical lines. In the preferred embodiment of the presentinvention as previously described, the curved surface of each of thecomposite reflectors is made up of a plastic supporting material such asis generally utilized for antenna radomes. One material suitable forthis purpose comprises woven glass fibers (commonly termed Fiberglas)impregnated with a polyester or epoxy resin. The plastic material istransparent to microwave energy and serves merely to support and toshape the metallic reflecting strips which are bonded to it, the bondedstrips comprising the active refleeting elements of the componentreflectors.

In FIG. 3, the solid lines indicate the location of metallic strips onthe upper surface of the unobstructed rearward plastic material asviewed in FIG. 3. The dashed lines represent the location of metallicreflecting elements on the upper surface of the rearward plasticmaterial in those areas where the rearward plastic is shadowed 'by theforward portions of the composite reflector. The dot-dashed linesrepresent the location of the metallic strips on the under side of theplastic material of the associated forward component antennas. Thestippled surface of FIG. 3 represents that surface which is common toboth of the component reflectors. The under side of the common surfaceis coated with a metal based paint or otherwise adapted to reflect allimpinging microwave energy irrespective of its polarization.

The location of the metallic strips on the upper or lower side of theirrespective component reflectors is arranged so that the microwave energyirradiating the reflector will travel the same predetermined electricaldistance to a respective reflector as would be the case were suchrespective reflectors utilized in the absence of the other componentreflector. It will be recognized that although the plastic supportingmaterial of the composite antenna is transparent to microwave energy,said material in general will have a dielectric constant which is otherthan that of air. The consequence is that the electrical path lengthtraversed by impinging rays of microwave energy, on the respectivemetallic strips oriented to reflect the polarization of the impingingrays will depend on whether the metallic strips being illuminated arebehind the transparent plastic material of the other componentreflector. In other words, despite the fact that the plastic supportingmaterial is transparent to microwave energy, its presence must be takeninto account in order that there be no phase front distortion of therefletced energy from each of the component reflectors.

In view of the fact that microwave energy must first pass through theforward component reflector before being reflected by the metallicstrips located on the rearward component reflector, provision is made soas to insure that all reflected microwave energy passes through twoequivalent thicknesses of the supporting plastic material in its travelfrom the radiating horn to the reflector and back into space.

By inspection of the front view of FIG. 3, it will be seen that thesurface of the horizontally disposed component reflector, outlined bylines 272817 and 1730-27, and the surface of the slanted componentreflector outlined by lines 17-31--32 and 32-33-17, are not shadowed bythe other component reflector. In such uncommon areas where there is noshading of one component reflector by the other, means must be providedto introduce the equivalent electrical length of the Plastic supportingmaterial. Such provision is made in the preferred embodiment of thepresent invention by adding sections of plastic material having nometallic reflecting strips bonded thereon, in the unshaded uncommonsurface regions of the composite reflector so as to stimulate the sameshading effect that takes place elsewhere in the uncommon surface areas.This is shown in the front elevation view of FIG. 8 to be describedlater.

A clearer comprehension of the shading of portions of one of thecomponent reflectors by portions of the other may be facilitated byinspection of FIG. 4 together with the associated end elevational viewof FIG. 5. The location of the feed horns, one (47) for the horizontalreflector and the other (48) for the slanted reflector are shown in thefront elevation of FIG. 4 and the end elevation of FIG. 4 and the endelevation of FIG. 5. Antenna supporting member 49, pedestal 50 and hornsupporting member 51 are also indicated in FIG. 5.

As previously discussed, the horizontally disposed component reflectoris adapted to reflect horizontally polarized microwave energy.Therefore, the reflecting strips bonded to the horizontal reflector aredisposed along horizontal lines. Said horizontally disposed metallicreflecting strips appear in the front elevation of FIG. 4 in those areaswhere they are bonded to the upper side of the unshaded region of thehorizontal component reflector. Similarly, the vertically disposedmetallic strips of the slanted reflector also appear in FIG. 4 in thoseareas where they are bonded to the upper surface of the unmasked regionof the slanted reflector.

No other metallic strips appear in the view of FIG. 4 for the reasonthat they are either bonded to the lower surface of a forward one of thecomponent reflectors or the upper surface of a rearward one of thecomponent reflectors. This may be seen by reference to the enlargedsection of FIG. 6 which is taken along the lines 66 of FIG. 4. It wasnoted that the component reflectors of the composite reflector intersectalong the line 12-17 of FIG. 4. The horizontally disposed componentreflector of FIG. 4 is represented by the curved segment 344tl35 whilethe slanted component reflector is represented by the curved segment36-40-37. Inasmuch as the curved surface of the horizontal reflectorlying on the left side of intersection line 1217 lies rearward of thecurved surface of the slanted component reflector, the reflecting stripsare bonded to the upper surface of the plastic supporting material ofthe horizontal reflector. One such strip 38 is shown in FIG. 6.

It will be observed, however, that to the right of intersection line1217, the curved surface of the horizontal reflector lies forward of theslanted reflector. Consequently, the reflector strip 39 is placed on thelower surface of the horizontal antenna to the right of intersectionline 1217 in order that impinging microwave energy traverses the samethickness of plastic supporting material irrespective of whether therays of said impinging energy are directed to the left or to the rightof intersection line 1217. To the left of the intersection line the raysmust pass through the region 3640 of the slanted reflector before beingreflected by strip 38. To the right of the intersection line the raysmust pass through an equivalent thickness of plastic material in theregion 40-35 of the horizontal reflector before being reflected by strip39.

The vertically disposed strips of the slanted reflector are positionedon the lower and upper surfaces of the plastic material of the slantedreflector in analagous fashion. Only the ends of the vertical stripsappear in FIG. 6. To the left of intersection line 12-17, said stripsare bonded to the lower surface of the plastic material of the slantedreflector while to the right of the intersection line the strips arebonded to the upper surface of the slanted reflector. When rays ofvertically polarized microwave energy impinge on the slanted reflectorto the left of the intersection line, they must pass twice through asingle thickness of the plastic supporting material of the slantedreflector in the region 3640. To the right of the intersection line therays of vertically polarized microwave energy must twice pass through asingle thickness of the region 40--35 of the horizontal antenna.Accordingly, the vertically disposed strips are mounted on the undersurface of the slanted reflector to the left of the intersection line,and on the upper surface of the slanted reflector to the right of theintersection line.

The location of the reflecting strips is further illustrated in theenlarged sectional view of FIG. 7 which is taken along the line 77 ofFIG. 4 lying to the right of intersection line 1217. The horizontallydisposed reflecting strips 41 are bonded to the lower surface of theforward portion of the horizontal component reflector. The verticallyoriented reflecting strips 42 are aflixed to the upper surface of therearward portion of the slanted component reflector. The lower surfaceof the common portion of the composite reflector between points 43 and44 is covered with a metal-based paint 45. Vertically disposedreflecting strips are bonded to the lower surface of the slanted antennain the region 4346.

FIG. 8 illustrates the addition of two sections of plastic material inthe uncommon unshaded regions of the composite antenna to create ashading effect similar to that obtaining elsewhere in the uncommonshaded regions. The plastic material is preferably added to the curvededge 17-5253 of the forward horizontal reflector and to the curved edge175455 of the forward slanted reflector of FIG. 4 so as to preclude thedirect irradiation by the feed horns 47 and 58 of the reflecting stripsin those unshaded areas of the component reflectors where the strips aremounted on upper plastic surfaces. FIG. 8 is cut away at the lowerextremities to expose the reflecting strips 56 and 57 now being shadedby the added plastic material.

Because the major axis of the horizontally disposed component reflectoris oriented along a horizontal line and inasmuch as said reflector isadapted to reflect horizontally polarized microwave energy, there is noproblem in illuminating the horizontally disposed component reflector bya conventional flared horn adapted to radiate horizontally polarizedmicrowave energy. In the case of the slanted component reflector,however, a problem arises in that the major axis of the slantedreflector is oriented at 45 relative to the polarization of themicrowave energy to be reflected by it. It can be seen that in the caseof the slanted reflector, its respectively associated illuminating hornmust be capable of radiating a generally fan-shaped beam of microwaveenergy whose major dimension lies along a line oriented at 45 to thedirection of energy polarization.

A suitably adapted feed horn capable of producing the required beamshape and energy polarization for the slanted reflector is shown in FIG.9. In FIG. 9, a linearly polarized wave of microwave energy is fed intothe throat of feed horn 58 by means of a conventional rectangularwaveguide adaptor (not shown). The linearly polarized energy isrepresented by the two orthogonal components 59 and 60 which share acommon amplitude and phase. The rectangular throat of horn 58 is flaredinto a larger rectangular radiating aperture 61.

Horn 58 may be considered as being a superposition of two rectangularhorns. By incorporating sets of parallel fins 62 and 63, two independentapertures are maintained. The microwave energy component represented bythe vector 59 sees a rectangular horn aperture having vertices designedby the numerals 64, while the other component of microwave energyrepresented by the vector 60 sees a rectangular horn aperture havingvertices designated by the numeral 65.

Upon the combination of these two orthogonally polarized waves in space,a resultant single field, represented by the vector 66, is realized. Theresultant vector 66 may be oriented at any arbitrary angle including theangle of 45 by the adjustment of mutual amplitude between the two inputorthogonal vectors 59 and 60. Additionally, an eliptically or circularlypolarized resultant microwave energy field may be produced in space bythe adjustment of mutual electrical phase between the input microwaveenergy components represented by vectors 59 and 60.

In short, when the horn aperture 61 major axis of symmetry is arrangedparallel to the slanted reflector axis of symmetry as shown in FIG. 4,there is achieved uniform illumination of the slanted reflector bymicrowave energy polarized along lines parallel to the verticalreflecting strips bonded to the slanted component reflector.

From the preceding it can be seen that the objects of the presentinvention have been achieved by the provision of a composite microwaveenergy directive element comprising two components reflectors, eachconforming in part to the same figure of revolution. The compositereflector is generated by the rotation of one of the componentreflectors, relative to the other, through a predetermined angle aboutthe axis of revolution of the figure of revolution. Positive electricalisolation of one component reflector from the other is achieved by theprovision of polarization sensitive reflecting elements such as stripswhich are bonded to the plastic supporting material of the respectivecomponent reflectors. In the disclosed pre-I ferred embodiment of thepresent invention, provision is made for the optimum location ofreflecting strips on their respective component reflectors so as toequalize path length traversed by impinging rays of microwave energyduring the course of travel from a respective one of a pair ofirradiating horns to the associated component reflector and then backout into space. Each of the horns is adapted to transmit microwaveenergy which is polarized orthogonally to the energy emitted by theother. Additionally, a specially suited horn is provided for the slantedcomponent reflector whereby the reflector illumination and energypolarization requirements are fully met.

It should be noted that although polarization-sensitive reflectingstrips have been shown mounted on the uncommon shaded surfaces of thecomponent reflector, said surfaces alternatively but less preferably maybe covered by a reflecting material insensitive and nondiscriminatory tothe polarization of incident microwave energy. Inasmuch as the forwardportions of the uncommon surface areas selectively reflected arespective one of the two orthogonally polarized beams, the rearwardshaded portions are irradiated primarily by only the othercrosspolarized one of the incident beams which passes through saidforward portions. However, as a practical matter, not all of theproperly polarized beam energy may be reflected by the strips on theforward surfaces. Therefore, if the rearward surfaces were totallyreflective, i.e., not polarization discriminatory, the undesired energycomponent which passes through the forward surfaces might give rise toobjectionable side lobes in the beam formed by the rearward surfaces.When both the forward and rearward surfaces are madepolarization-sensitive, the impoperly passed energy component whichpenetrates the forward reflecting surfaces is readily passed also by therearward surfaces which is adapted to maximally reflect energy polarizedorthogonally to the improperly passed component.

For the sake of simplicity and clarity, two identically shaped componentreflectors are utilized in the illustrated embodiment of the compositereflector. It should be understood, however, that the componentreflectors need not be identical provided that each contains a surfaceportion which is conformal to the same figure of revolution. Theremaining surface portions may be independently shaped to meet therequirements of the individual beam patterns which each componentreflector is to respectively generate.

While the invention has been described in its preferred embodiments, itis to be understood that the words which have been used are words ofdescription rather than of limitation and that changes within thepurview of the appended claims may be made without departing from thetrue scope and spirit of the invent-ion in its broader aspects.

What is claimed is:

1. A composite microwave energy directive element comprising twocomponent microwave energy directive elements, each containing a surfaceportion which is conformal to the same surface of revolution, one ofsaid directive elements being rotated through a predetermined anglerelative to the other about the axis of revolution of said surface ofrevolution, said composite element containing a surface portion of saidsurface of revolution Which is common to both of said componentelements, each of said component elements being adapted to direct only apredetermined one of two orthogonally polarized incident beams ofmicrowave energy.

2. A superimposed polarization isolated shaped reflector formicrowaveenergy comprising two component microwave energy reflectors, eachcontaining a surface portion which is conformed to the same surface ofrevolution, one of said reflectors being rotated through a predeterminedangle relative to the other about of the axis of revolution of saidsurface of revolution, said superimposed reflector containing a surfaceportion which is conformal to said surface of revolution and common toboth of said component reflectors, each of said component reflectorsbeing adapted to reflect only a predetermined one of two orthogonallypolarized incident beams of microwave energy. 1

3. A composite microwave energy directive element comprising twocomponent microwave energy directive elements, each containing a surfaceportion which is conformal to the same surface of revolution, one ofsaid directive elements being rotated through a predetermined anglerelative to the other about the axis of revolution of said surface ofrevolution, said composite element containing a first surface portion ofsaid surface of revolution which is common to both of said componentelements, and second surface portions uniquely associated with arespective one of said component elements, said common portion beingadapted to direct both of two orthogonally polarized incident beams ofmicrowave energy, and said uniquely associated portions being adapted todirect only a respective one of said two incident beams.

4. A superimposed polarization isolated shaped reflector for microwaveenergy comprising two component microwave energy reflectors, eachcontaining a surface portion which is conformal to the same surface ofrevolution, one of said reflectors being rotated through a predeterminedangle relative to the other about the axis of revolution of said surfaceof revolution, said superimposed reflector containing a first surfaceportion which is comformal to said surface of revolution and common toboth of said component reflectors, and second surface portions uniquelyassociated with a respective one of said component reflectors, saidcommon portion being adapted to reflect both of two orthogonallypolarized incident beams of microwave energy, and said uniquelyassociated portions being adapted to reflect only a respective one ofsaid two incident beams.

5. A superimposed polarization isolated shaped reflector for microwaveenergy for use in a V-beam radar system, comprising two componentmicrowave energy reflectors, each containing a surface portion which isconformal to the same paraboloidal surface of revolution, one of saidreflectors being rotated through an angle of substantially 45 relativeto the other about the axis of revolution of said surface of revolution,said superimposed reflector containing a first surface portion which isconformal to said paraboloidal surface of revolution and common to bothof said component reflectors and second surface portions uniquelyassociated with a respective one of said component reflectors, saidcommon portion being adapted to reflect both of two orthogonallypolarized incident beams of microwave energy and said uniquelyassociated portions being adapted to reflect a respective one of saidtwo incident beams whereby mutually independent reflected beams oforthogonally polarized microwave energy are produced in space.

6. A superimposed polarization isolated shaped reflector for microwaveenergy comprising two component shaped supporting members, each memberconsisting of material transparent to incident beams of orthogonallypolarized microwave energy, each of said members containing a surfaceportion which is conformal to the same surface of revolution and havingan axis of symmetry bisecting said surface of revolution, one of saidmembers being rotated through a predetermined angle relative to theother about the axis of revolution of said surface of revolution, saidmembers, after rotation, containing a surface portion which is conformalto said surface of revolution and common to both and uniquely associatedaddi tional surface portions, first means conformably mounted on saidcommon portion for reflecting both beams of said orthogonally polarizedmicrowave energy, second means conformably mounted on said additionalsurface portions of one of said members for selectively reflecting onlya predetermined one of said orthogonally polarized beams, third meansconformably mounted on said additional surface portions of the other ofsaid members for selectively reflecting only the other of saidorthogonally polarized beams, and first and second means forrespectively illuminating said first and second members with saidorthogonally polarized microwave energy.

7. Apparatus as defined in claim 6 wherein one of said illuminatingmeans is adapted to emit a linearly polarized beam of microwave energyhaving a plane of polarization obliquely related to the axis of symmetryof one of said members.

8. A composite microwave energy directive element for use in a V-beamradar system comprising two component shaped supporting members, eachmember containing a surface portion which is comformal to the samesurface of revolution and consisting of material transparent to incidentbeams of orthogonally polarized microwave energy, one of said membersbeing rotated through a predetermined angle relative to the other aboutthe axis of revolution of said surface of revolution, said members,after rotation, containing a surface portion which is conformal to saidsurface of revolution and common to both and uniquely associatedadditional surface portions, first means conformably mounted on saidcommon portion for reflecting both beams of said orthogonaly polarizedmicrowave energy, second means conformably mounted on said additionalsurface portions of one of said members for selectively reflecting onlya predetermined one of said orthogonally polarized beams, and thirdmeans conformably mounted on said additional surface portions of theother of said members for selectively reflecting only the other of saidorthogonally polarized beams whereby mutually independent reflectedbeams of orthogonally polarized microwave energy are produced in space.

9. Apparatus as defined in claim 8 wherein said second and thirdselectively reflecting means are mounted on the respective surfaces ofthe associated ones of said supporting members so as to equalize theelectrical path length traversed by said incident beams of microwaveenergy during the course of production of said mutually independentreflected beams.

References Cited in the file of this patent UNITED STATES PATENTS2,430,568 Hershberger Nov. 11, 1947 2,522,562 Blitz Sept. 19, 19502,726,389 Taylor Dec. 6, 1955

5. A SUPERIMPOSED POLARIZATION ISOLATED SHAPED REFLECTOR FOR MICROWAVEENERGY FOR USE ON A V-BEAM RADAR SYSTEM COMPRISING TWO COMPONENTMICROWAVE ENERGY REFLECTORS, EACH CONTAINING A SURFACE PORTION WHICH ISCONFORMAL TO THE SAME PARABOLOIDAL SURFACE OF REVOLUTION, ONE OF SAIDREFLECTORS BEING ROTATED THROUGH AN ANGLE OF SUBSTANTIALLY 45* RELATIVETO THE OTHER ABOUT THE AXIS OF REVOLUTION OF SAID SURFACE OF REVOLUTION,SAID SUPERIMPOSED REFLECTOR CONTAINING A FIRST SURFACE PORTION WHICH ISCONFORMAL TO SAID PARABOLOIDAL SURFACE OF REVOLUTION AND COMMON TO BOTHOF SAID COMPONENT REFLECTORS AND SECOND SURFACE PORTIONS UNIQUELYASSOCIATED WITH A RESPECTIVE ONE OF SAID COMPONENT REFLECTORS, SAIDCOMMON PORTION BEING ADAPTED TO REFLECT BOTH OF TWO ORTHOGONALLYPOLARIZED INCIDENT BEAMS OF MICROWAVE ENERGY AND SAID UNIQUELYASSOCIATED PORTIONS BEING ADAPTED TO REFLECT A RESPECTIVE ONE OF SAIDTWO INCIDENT BEAMS WHEREBY MUTUALLY INDEPENDENT REFLECTED BEAMS OFORTHOGONALLY POLARIZED MICROWAVE ENERGY ARE PRODUCED IN SPACE.